Recently, digital cameras have become very popular, along with personal computers that process image information from imaging systems. More compact and less expensive digital cameras and imaging systems are being demanded, and these demands have been addressed by developing more compact and less expensive imaging lenses. For example, Japanese Laid-Open Patent Application 2000-258684 discloses an imaging lens that includes, in order from the object side, a negative lens element and a positive lens component with a sufficient back focus distance, with a short focal length, and with at least one lens surface of the negative lens element being an aspheric lens surface. However, the imaging lens of this published Japanese application is not sufficiently compact. Greater compactness, as well as a more inexpensive imaging lens, is needed.
Previously in digital cameras, it has been necessary to use small optical elements that allow a principal ray to enter at an angle of incidence within about fifteen degrees to the normal of the imaging plane because of the light detecting properties of the image pickup elements used with the imaging lens. Recently however, the use of principal rays with angles of incidence larger than about fifteen degrees have become acceptable with some image pickup elements now available. Accordingly, the development of an imaging lens that is capable of correcting aberrations with the principal ray having a larger angle of incidence is desired.
The present invention relates to a fixed focus imaging lens that is compact, is of inexpensive construction, favorably corrects aberrations, and is particularly designed for use in digital cameras and imaging systems used with personal computers and portable electronic equipment.